Cholesterol in Pancreatic β-Cell Death and Dysfunction: Underlying Mechanisms and Pathological Implications

The role of non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (nhhr) in prediabetes progression and the mediating effect of BMI: a longitudinal study in China

BACKGROUND

Diabetes prevalence in China is significant, with a large proportion in the prediabetes stage. Dyslipidemia is associated with abnormal glucose metabolism, and the non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) shows potential in diabetes risk assessment, but its role in prediabetes progression is understudied.

METHODS

A longitudinal study from 2011 to 2015 using CHARLS data was conducted. After exclusions, 1408 participants were included. NHHR was calculated from serum TC and HDL - C levels. Diabetes and prediabetes were defined based on standard criteria. Covariates and mediators were assessed, and statistical analyses included logistic regression and mediation analysis, and mediation analysis was conducted to evaluate the involvement of BMI in the association between NHHR and the risk of prediabetes progression.

RESULTS

Among the 1423 people in the cohort analysis, 339 (23.8%) were diagnosed with prediabetes progression. The median NHHR was significantly larger in the progression group (136.99 vs. 124.95, p < 0.05). In the fully adjusted model, NHHR one-unitincrease led to a 10% higher risk. Subgroup analyses showed consistent associations in most subgroups. BMI mediated 33.8% of the NHHR - prediabetes progression association.

CONCLUSION

NHHR is correlated with the risk of prediabetes progressing to diabetes, and BMI may mediate this association. NHHR monitoring could help assess the risk of progression in prediabetes participants.

Non-linear relationship between arteriosclerosis index and diabetes risk in non-obese east Asian adults

Previous studies have shown a positive association between the arteriosclerosis index (AI) and future diabetes risk. However, evidence in non-obese populations is limited. This study investigates the relationship between AI and future diabetes risk in non-obese East Asian adults. This retrospective cohort study enrolled 95,402 non-obese adults from China and Japan. Participants had a mean age of 42.92 ± 12.24 years, with 51,295 (53.77%) being male. Median follow-up was 3.01 years. Cox proportional hazards models assessed the association between baseline AI and diabetes risk. Non-linear associations were explored using cubic splines and smoothed curves in Cox models. Sensitivity analyses were performed. After adjusting for covariates, a positive association was found between AI and diabetes risk in non-obese adults (HR 1.09, 95% CI 1.03-1.15, P = 0.0017). A non-linear relationship was identified, with an inflection point at 1.47. Below this point, HR was 5.87 (95% CI 1.20-28.63, P = 0.0287); above, it was 1.07 (95% CI 1.02-1.13, P = 0.0115). Sensitivity analyses affirmed the robustness of these results. This study identifies a positive, non-linear association between the AI and diabetes risk in non-obese adults. Interventions targeting AI reduction could significantly lower the risk of future diabetes in this population.

Proprotein convertase subtilisin/kexin type 9 deficiency in extrahepatic tissues: emerging considerations

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is primarily secreted by hepatocytes. PCSK9 is critical in liver low-density lipoprotein receptors (LDLRs) metabolism. In addition to its hepatocellular presence, PCSK9 has also been detected in cardiac, cerebral, islet, renal, adipose, and other tissues. Once perceived primarily as a "harmful factor," PCSK9 has been a focal point for the targeted inhibition of both systemic circulation and localized tissues to treat diseases. However, PCSK9 also contributes to the maintenance of normal physiological functions in numerous extrahepatic tissues, encompassing both LDLR-dependent and -independent pathways. Consequently, PCSK9 deficiency may harm extrahepatic tissues in close association with several pathophysiological processes, such as lipid accumulation, mitochondrial impairment, insulin resistance, and abnormal neural differentiation. This review encapsulates the beneficial effects of PCSK9 on the physiological processes and potential disorders arising from PCSK9 deficiency in extrahepatic tissues. This review also provides a comprehensive analysis of the disparities between experimental and clinical research findings regarding the potential harm associated with PCSK9 deficiency. The aim is to improve the current understanding of the diverse effects of PCSK9 inhibition.

The association between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio with type 2 diabetes mellitus: recent findings from NHANES 2007-2018

OBJECTIVE

This study aims to assess the relationship between NHHR (non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio) and Type 2 diabetes mellitus (T2DM) in US adults, using National Health and Nutrition Examination Survey (NHANES) data from 2007 to 2018.

METHODS

This study explored the connection between NHHR and T2DM by analyzing a sample reflecting the adult population of the United States (n = 10,420; NHANES 2007-2018). NHHR was characterized as the ratio of non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol. T2DM was defined based on clinical guidelines. This research used multivariable logistic models to examine the connection between NHHR and T2DM. Additionally, it included subgroup and interaction analyses to assess variations among different groups. Generalized additive models, smooth curve fitting, and threshold effect analysis were also employed to analyze the data further.

RESULTS

The study included 10,420 subjects, with 2160 diagnosed with T2DM and 8260 without. The weighted multivariate logistic regression model indicated an 8% higher probability of T2DM for each unit increase in NHHR (OR: 1.08, 95% CI: 1.01-1.15) after accounting for all covariates. Subgroup analysis outcomes were uniform across various categories, demonstrating a significant positive relationship between NHHR and T2DM. Interaction tests showed that the positive link between NHHR and T2DM remained consistent regardless of age, body mass index, smoking status, moderate recreational activities, hypertension, or stroke history, with all interaction P-values exceeding 0.05. However, participants' sex appeared to affect the magnitude of the connection between NHHR and T2DM (interaction P-value < 0.05). Also, a nonlinear association between NHHR and T2DM was discovered, featuring an inflection point at 1.50.

CONCLUSIONS

Our study suggests that an increase in NHHR may be correlated with a heightened likelihood of developing T2DM. Consequently, NHHR could potentially serve as a marker for estimating the probability of T2DM development.

Nonalcoholic fatty liver disease aggravates acute pancreatitis through bacterial translocation and cholesterol metabolic dysregulation in the liver and pancreas in mice

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is an independent risk factor for severe acute pancreatitis (AP). The underlying mechanism remains unclear. We sought to determine how bacterial translocation and cholesterol metabolism in the liver and pancreas affect the severity of AP in NAFLD mice.

METHODS

C57BL/6N mice were fed on a high-fat diet (HFD) to generate the NAFLD model, and mice in the control group were provided with a normal diet (ND). After being anesthetized with ketamine/xylazine, mice got a retrograde infusion of taurocholic acid sodium into the pancreatic duct to induce AP, and sham operation (SO) was used as control. Serum amylase and Schmidt's pathological score system were used to evaluate AP severity. Bacterial loads, total cholesterol level, and cholesterol metabolic-associated molecules [low-density lipoprotein receptor (LDLR) and ATP-binding cassette transporter A1 (ABCA1)] were analyzed in the liver and pancreas.

RESULTS

Compared with the ND-AP group, mice in the HFD-AP group had severer pancreatitis, manifested with higher serum amylase levels and higher AP pathologic scores, especially the inflammation and hemorrhage scores. Compared with the HFD-SO group and ND-AP group, bacterial loads in the liver and pancreas were significantly higher in the HFD-AP group. Mice in the HFD-AP group showed a decreased LDLR expression and an increased ABCA1 expression in the pancreas, although there was no significant difference in pancreas total cholesterol between the HFD-AP group and the ND-AP group.

CONCLUSIONS

NAFLD aggravates AP via increasing bacterial translocation in the liver and pancreas and affecting pancreas cholesterol metabolism in mice.

The association between circulatory, local pancreatic PCSK9 and type 2 diabetes mellitus: The effects of antidiabetic drugs on PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent modulator of cholesterol metabolism and plays a crucial role in the normal functioning of pancreatic islets and the progression of diabetes. Islet autocrine PCSK9 deficiency can lead to the enrichment of low-density lipoprotein (LDL) receptor (LDLR) and excessive LDL cholesterol (LDL-C) uptake, subsequently impairing the insulin secretion in β-cells. Circulatory PCSK9 levels are primarily attributed to hepatocyte secretion. Notably, anti-PCSK9 strategies proposed for individuals with hypercholesterolemia chiefly target liver-derived PCSK9; however, these anti-PCSK9 strategies have been associated with the risk of new-onset diabetes mellitus (NODM). In the current review, we highlight a new direction in PCSK9 inhibition therapy strategies: screening candidates for anti-PCSK9 from the drugs used in type 2 diabetes mellitus (T2DM) treatment. We explored the association between circulating, local pancreatic PCSK9 and T2DM, as well as the relationship between PCSK9 monoclonal antibodies and NODM. We discussed the emergence of artificial and natural drugs in recent years, exhibiting dual benefits of antidiabetic activity and PCSK9 reduction, confirming that the diverse effects of these drugs may potentially impact the progression of diabetes and associated disorders, thereby introducing novel avenues and methodologies to enhance disease prognosis.

Effect of Triglyceride-Glucose Indices and Circulating PCSK9-Associated Cardiovascular Risk in STEMI Patients with Primary Percutaneous Coronary Artery Disease: A Prospective Cohort Study

Background and Aims

This study aimed to determine whether convertase subtilisin/kexin type 9 (PCSK9)-associated cardiovascular risk is modulated by triglyceride-glucose (TyG) in ST-segment elevation myocardial infarction (STEMI) patients with primary percutaneous coronary disease (PCI).

Methods

A total of 1541 patients with STEMI (aged ≥18 years) undergoing primary PCI were consecutively enrolled between March 2017 and March 2019.

Outcomes

When stratifying the overall population according to TyG indices less than or greater than the median (TyG median = 9.07) as well as according to quartiles of PCSK9 levels, higher TyG index levels were significantly associated with all-cause mortality only when TyG levels were 9.07 or higher (ie, relative to quartile 1 [Q1], the adjusted HR for all-cause mortality was 3.20 [95% CI, 0.54-18.80] for Q2, p = 0.199; 7.89 [95% CI, 1.56-40.89] for Q3, p = 0.013; and 5.61 [95% CI, 1.04-30.30] for Q4, p = 0.045. During a median follow-up period of 1.96 years, the HR for all-cause mortality was higher in the subset of patients with TyG ≥median and PCSK9 ≥median (p for trend = 0.023) among those with type 2 diabetes mellitus (T2DM). However, there were no statistically significant differences among the subgroups. Among T2DM patients with a TyG index greater than the median, the Kaplan-Meier curve showed that patients with the highest PCSK9 levels had an increased risk of all-cause mortality (log-rank p = 0.017) and cardiac-cause mortality (log-rank p = 0.037) compared with lower PCSK9 quartile levels.

Conclusion

Elevated PCSK9 levels are related to all-cause mortality and cardiac-related mortality when TyG levels are greater than the median, but not when levels are less than the median. This suggests a potential benefit of lowering circulating PCSK9 levels in STEMI patients with insulin resistance.

Glucokinase activation as antidiabetic therapy: effect of nutraceuticals and phytochemicals on glucokinase gene expression and enzymatic activity

Diabetes represents an important public health problem. Recently, new molecular targets have been identified and exploited to treat this disease. Due to its pivotal role in glucose homeostasis, glucokinase (GCK) is a promising target for the development of novel antidiabetic drugs; however, pharmacological agents that modulate GCK activity have been linked to undesirable side-effects, limiting its use. Interestingly, plants might be a valuable source of new therapeutic compounds with GCK-activating properties and presumably no adverse effects. In this review, we describe biochemical characteristics related to the physiological and pathological importance of GCK, as well as the mechanisms involved in its regulation at different molecular levels. Posteriorly, we present a compendium of findings supporting the potential use of nutraceuticals and phytochemicals in the management of diabetes through modulation of GCK expression and activity. Finally, we propose critical aspects to keep in mind when designing experiments to evaluate GCK modulation properly.

Whole Egg Consumption Impairs Insulin Sensitivity in a Rat Model of Obesity and Type 2 Diabetes

BACKGROUND

The literature regarding the relation between egg consumption and type 2 diabetes (T2D) is inconsistent and there is limited evidence pertaining to the impact of egg consumption on measures of insulin sensitivity.

OBJECTIVES

The aim of this study was to investigate the effect of dietary whole egg on metabolic biomarkers of insulin resistance in T2D rats.

METHODS

Male Zucker diabetic fatty (ZDF) rats (n = 12; 6 wk of age) and age-matched lean controls (n = 12) were randomly assigned to be fed a casein- or whole egg-based diet. At week 5 of dietary treatment, an insulin tolerance test (ITT) was performed on all rats and blood glucose was measured by glucometer. After 7 wk of dietary treatment, rats were anesthetized and whole blood was collected via a tail vein bleed. Following sedation, the extensor digitorum longus muscle was removed before and after an intraperitoneal insulin injection, and insulin signaling in skeletal muscle was analyzed by Western blot. Serum glucose and insulin were analyzed by ELISA for calculation of the homeostatic model assessment of insulin resistance (HOMA-IR).

RESULTS

Mean ITT blood glucose over the course of 60 min was 32% higher in ZDF rats fed the whole egg-based diet than in ZDF rats fed the casein-based diet. Furthermore, whole egg consumption increased fasting blood glucose by 35% in ZDF rats. Insulin-stimulated phosphorylation of key proteins in the insulin signaling pathway did not differ in skeletal muscle of ZDF rats fed casein- and whole egg-based diets. In lean rats, no differences were observed in insulin tolerance, HOMA-IR and skeletal muscle insulin signaling, regardless of experimental dietary treatment.

CONCLUSIONS

These data suggest that whole body insulin sensitivity may be impaired by whole egg consumption in T2D rats, although no changes were observed in skeletal muscle insulin signaling that could explain this finding.

Prenatal exposure to diesel exhaust PM2.5 causes offspring β cell dysfunction in adulthood

Environmental stressors that encounter in early-life and cause abnormal fetal and/or neonatal development may increase susceptibility to non-communicable diseases such as diabetes. Maternal exposure to ambient fine particulate matter (PM_2.5) is associated with various fetal abnormalities, suggesting that it may program offspring's susceptibility to diabetes. In the present study, we therefore examined whether maternal exposure to diesel exhaust PM_2.5 (DEP), one of the major sources of ambient PM_2.5 in urban areas, programs adult offspring's glucose metabolism. Female C57Bl/6J mice were intratracheally instilled with DEP or vehicle throughout a 7-wk preconceptional period, gestation, and lactation, and the glucose homeostasis of their adult male offspring was assessed. Intraperitoneal glucose tolerance test (IPGTT) revealed that the maternal exposure to DEP significantly impaired adult male offspring's glucose tolerance. Unexpectedly, it did not influence their insulin sensitivity, whereas it significantly decreased their glucose-induced insulin secretion (GIIS). This deficit in insulin secretion was corroborated by their significant decrease in arginine-induced insulin secretion. Histological analysis demonstrated that the deficit in insulin secretion was accompanied by the decrease in pancreatic islet and β cell sizes. To differentiate the effects of maternal exposure to DEP before birth and during lactation, some offspring were cross-fostered once born. We did not observe any significant effect of cross-fostering on the glucose homeostasis of adult male offspring and the function and morphology of their β cells. Prenatal exposure to DEP programs the morphology and function of β cells and thus homeostatic regulation of glucose metabolism in adult male offspring.

Mice Fed a High-Cholesterol Diet Supplemented with Quercetin-3-Glucoside Show Attenuated Hyperlipidemia and Hyperinsulinemia Associated with Differential Regulation of PCSK9 and LDLR in their Liver and Pancreas

SCOPE

Hepatic LDL receptor (LDLR) and proprotein convertase subtilisin/kexin type 9 (PCSK9) regulate the clearance of plasma LDL-cholesterol (LDL-C): LDLR promotes it, and PCSK9 opposes it. These proteins also express in pancreatic β cells. Using cultured hepatocytes, we previously showed that the plant flavonoid quercetin-3-glucoside (Q3G) inhibits PCSK9 secretion, stimulated LDLR expression, and enhanced LDL-C uptake. Here, we examine whether Q3G supplementation could reverse the hyperlipidemia and hyperinsulinemia of mice fed a high-cholesterol diet, and how it affects hepatic and pancreatic LDLR and PCSK9 expression.

METHODS AND RESULTS

For 12 weeks, mice are fed a low- (0%) or high- (1%) cholesterol diet (LCD or HCD), supplemented or not with Q3G at 0.05 or 0.1% (w/w). Tissue LDLR and PCSK9 is analyzed by immunoblotting, plasma PCSK9 and insulin by ELISA, and plasma cholesterol and glucose by colorimetry. In LCD-fed mice, Q3G has no effect. In HCD-fed mice, it attenuates the increase in plasma cholesterol and insulin, accentuates the decrease in plasma PCSK9, and increases hepatic and pancreatic LDLR and PCSK9. In cultured pancreatic β cells, however, it stimulates PCSK9 secretion.

CONCLUSION

In mice, dietary Q3G could counter HCD-induced hyperlipidemia and hyperinsulinemia, in part by oppositely modulating hepatic and pancreatic PCSK9 secretion.

Effect of LDL cholesterol, statins and presence of mutations on the prevalence of type 2 diabetes in heterozygous familial hypercholesterolemia

Patients with heterozygous familial hypercholesterolemia (HeFH) have been reported to be less vulnerable to type 2 diabetes mellitus (T2DM), although the mechanism is unknown. The aims of the present study were to assess the effects of low density lipoprotein (LDL) cholesterol concentration and the presence of FH-causing mutations on T2DM prevalence in HeFH. Data were collected from the Dyslipidemia Registry of the Spanish Arteriosclerosis Society. Inclusion criteria were definite or probable HeFH in patients aged ≥18 years. T2DM prevalence in HeFH patients was compared with data of the general population. 1732 patients were included. The prevalence of T2DM was lower in patients with HeFH compared with the general population (5.94% vs 9.44%; OR: 0.606, 95% CI 0.486-0.755, p < 0.001). Risk factors for developing T2DM were male sex, age, body mass index, hypertension, baseline triglyceride levels and years on statin therapy. The prevalence of T2DM in HeFH patients was 40% lower than that observed in the general population. Gene mutations and LDL cholesterol concentrations were not risk factors associated with the prevalence of T2DM in patients with HeFH. The prevalence of T2DM in patients with HeFH was 40% lower than in the general population matched for age and sex.